Throughout the years the industry has made efforts to increase the yield of meat on the legs that are separated from the back portion. By way of example, known apparatus for executing such method includes a conveyor line with shackles for conveying a series of poultry carcass parts suspended from the shackles, and at least one cutting device for making an incision in the joints connecting the legs to the back portion. After making the incision the legs can be torn loose from the back portion.
U.S. Pat. No. 4,639,975 (priority 1984) already had as objective to separate the leg with the oyster remaining on top thereof and not on the back part of the bird, which is less suitable for consumption. It applied leg guides and cutting knives attached to the guide edges.
EP-B-0 369 544 (priority 1988) provided better yield by improving the accuracy of the incision by gripping the back portion of the carcass by a gripping member proceeding in a closed conveyor loop at higher speeds than the overhead conveyor for the poultry carcasses, and by application of guide means to guide the back portion of the carcasses until after the back has been removed from the thighs.
U.S. Pat. No. 5,176,563 (priority 1990) worked on the incision. As a result of the groin incision, a large part of the tissue connections between body part and legs remain intact. It proposed to position the carcass part relative to the incision means and making a groin incision between the legs and the body part at the side of the legs facing the body part. Following that the legs were dislocated from the joints and pulled off the body part.
U.S. Pat. No. 5,188,559 (priority 1991) proposed to reliably and cleanly separate the backs from the legs of the poultry carcasses and leave the oysters of the joints attached to the separated ends of the thighbones. For this purpose a first pair of incisions were made at the locations of the thigh joints, the back portion of the carcass was rotated relative to the legs for dislodging the ball from the sockets of the thigh joints, and the back portion of the carcass was pulled away from the legs at the location of the thigh joints.
U.S. Pat. No. 6,322,438 (priority 1999) tried to improve the yield of meat on the legs by a more accurate guiding of the poultry carcasses to the cutters, which cut through the tissue extending between the thighs and the back portions of the carcasses.
US 2005/0059334 (priority 2003) improves the yield of the meat on the legs by a combination of hold down bars, guide members, blades, and plowing members to effect a yield value increase for the whole leg by increasing the amount of flesh and skin removed from the back portion and left attached to the upper thigh portion of the whole leg.
The picture that transpires from the prior art during the last decades is that the problem of improving the yield of meat on the leg that is separated from a back portion has remained unsolved, and this despite all the efforts that numerous inventors have spent during these decades to solve this problem. One apparent problem for increasing this yield of meat is the accuracy with which the incision can be made at the location of the joints connecting the legs to the back portion of the poultry carcass part.